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   Ageratum conyzoides (草本植物) English   
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         一般影响

    农业:藿香蓟(Ageratum conyzoides)是许多一年生和多年生农作物的杂草,据报告,是许多农作物疾病的宿主(Ekeleme等人, 2005)。此杂草会干扰农作物生长和产量,因此对生态和经济产生重大影响(Singh 等人, 2001,Batish等人, 2009)。例如,在亚洲,水稻产量一直与藿香蓟(A. conyzoides)密度负相关(罗德等人, 1998)。有研究显示,此杂草具有植物相克作用,但是,幼苗对光线的竞争似乎是干扰作物的主要方式(Ekeleme等人, 2005)。
    植物相克:植物相克作用是一种生物干扰,一种植物将生物活性代谢物释放到周围的环境,对附近的植被生长,产生不利的影响,并对释放的植物产生选择优势(Batish等人, 2009a)。藿香蓟(A. conyzoides)的挥发性物质,包括早熟素及其衍生物单萜和倍半萜,会产生光抑制和植物相克作用。有许多证据显示,藿香蓟(A. conyzoides)产生的化学物质,会经由其根茎系统,抑制其它植物发芽和生长。藿香蓟(A. conyzoides)新鲜的叶片和挥发性油,会抑制各种作物幼苗生长(Kong等人,99),包括花生,红萝卜,黄瓜和黑麦草(Kong Hu & Xu 2002)。研究显示,藿香蓟(A. conyzoides)的芽萃取物,会抑制发芽尾穗苋中,马唐和生菜(莴苣)。答:萃取物藿香蓟(A. conyzoides)抑制小麦和水稻的种子发芽(Jha & Dhakal 1990,Ming 1999)。藿香蓟(A. conyzoides)叶片分泌和残留的酚,会干扰小麦的生长和发展(Singh 等人, 2003,Batish等人, 2009a)。生长在藿香蓟(A. conyzoides)根际土壤中的水稻,其根与芽的长度和生物量会显著减少18至30% (Batish等人, 2009a)。藿香蓟(A. conyzoides)的腐叶会影响水稻初期生长(Batish等人, 2009b)。最后,藿香蓟(A. conyzoides)会减少鹰嘴豆生长发育和结瘤(Batish等人, 2004)。当植物生长在营养不足的环境,和因为真菌感染或蚜虫啃食而减少时,光抑制和植物相克作用会提高(Kong Hu & Xu 2002)。
    植物病原传播:Kashina、Mabagala和Mpunami(2003)在坦桑尼亚附近的西红柿农场发现,藿香蓟(A. conyzoides)是「西红柿黄化卷叶病毒」的宿主杂草和病原库(Kashina,Mabagala & Mpunami 2003)。藿香蓟(A. conyzoides)可能是「西红柿黄化卷叶病毒」重要的病原库,因为它在西红柿农场内数量很多,它与粉虱载体共域,粉虱会自然地感染这种病毒。在其它地方,藿香蓟(A. conyzoides)已被确定为「藿香黄脉病毒」的宿主
    人类健康:藿香蓟(A. conyzoides)会造成某些人的过敏反应(Negi & Hajra 2007),并可能危害人类健康(Kohli & Batish 1996)。
    喜马拉雅植物族群案例研究:Shivilak位于印度北部喜马拉雅山区,素以丰富的植物多样性闻名。但是,藿香蓟(A. conyzoides)对天然植物草原结构和森林社群以及自然生态系统的动态,造成威胁(Singh 等人,;Dogra 等人, 2009)。此杂草取代了原生草被和重要的药用植物,研究显示它降低了生物量,生物多样性,使植群单一化(Dogra 等人, 2009)。它还会负面地干扰农作物(小麦,鹰嘴豆,大米,玉米和甘蔗)。



         地点特有的影响:
    Asia English 
    传播疾病: Yellow vein disease of Ageratum conyzoides, a weed species that is widely distributed throughout Asia, has been attributed to infection by the geminivirus Ageratum yellow vein virus (AYVV). Members of the Geminiviridae genus Begomovirus (Briddon and Markham 1995, in Saunders & Stanley 1999) are transmitted by the whitefly Bemisia tabaci (Gennadius) to a wide range of vegetable and fibre crops worldwide in which they cause serious diseases (Brown 1994, in Saunders & Stanley 1999).
    A. conyzoides plants coinfected with AYVV DNA A and DNA 1 remain asymptomatic, indicating that additional factors are required to elicit yellow vein disease. The author's results provide direct evidence for recombination between distinct families of plant single-stranded DNA viruses and suggest that coinfection by geminivirus and nanovirus-like pathogens may be a widespread phenomenon. The ability of plant DNA viruses to recombine in this way may greatly increase their scope for diversification.
    South East Asia (Asia) English 
    传播疾病: Weed species are believed to act as reservoir hosts for many economically important plant viral diseases. A. conyzoides, a weed that occurs throughout South East Asia, frequently exhibits yellow vein symptoms that are associated with infection by Ageratum Yellow Vein Virus (Saunders et al. 2000).

    农业: A. conyzoides is one of the most dominant weeds in upland crop areas of South East Asia (Kato-Noguchi 2001).
    South China (China) English 
    农业: The fresh leaves and volatile oil of A. conyzoides in south China were found to be highly inhibitory to seedling growth of various cultivated crops, especially in an adverse habitat.
    India English 
    其它: A. conyzoides poses a human health hazard also (Kohli & Batish 1996). A number of health problems in human beings and toxicity to livestock have been reported. These include contact dermatitis, skin irritation, nausea, giddiness (due to their pungent smell), and respiratory problems such as bronchitis and asthma.

    农业: A. conyzoides interferes with crops and causes yield reductions of major staple crops of India (Kohli et al. 2006). It forms thick monospecific stands at the expense of commonly grown crop species such as wheat, chickpea, rice and maize (Kohli et al. 2006, in Batish et al. 2009a). When it invades rangeland areas, it out competes native grasses causing scarcity of fodder (Kohli et al. 2006), thereby putting livestock under starvation conditions. Severe infestations by A. conyzoides reduces crop yields significantly and to such a low level that some farmers in the lower Shivalik ranges of the Himalayas have had to abandon their fields (Batish et al. 2004; Kohli & Batish 1996).

    降低本地生物多样性: Rich medicinal plants, an important resource, are being out-competed by A. conyzoides (Kohli & Batish 1996).
    Shivalik Ranges (India) English 
    人类健康: A. conyzoides presents a health hazard to humans (Batish 2008).

    农业: The weed is a problem for farmers, ecologists, locals, environmentalists and animals (Batish 2008). It is a troublesome weed of cultivated lands. A. conyzoides is responsible for replacing grasses in pastures and causing fodder loss (as cattle do not feed on the weed), deteriorating soil quality and reducing crop quality and yield (wheat, chickpea, rice, maize, and sugarcane) (Singh Undated). A. conyzoides also adversely affects animal health; and causes hindrances to ploughing (Batish 2008).

    改变水文: A. conyzoides chokes water channels (Singh Undated).

    改变营养机制: A. conyzoides deteriorates soil quality (Batish 2008). The weed is strongly allelopathic and adversely affects crop productivity through its allelochemicals. Almost all parts of the weed (stem, roots, leaves, inflorescence), are known to cause allelopathic effects. Volatile allelochemicals include Precocene I, Precocene II and Caryophyllene etc. Non-volatile phenolic acids include gallic acid, coumalic acid, and protocatechuic acid, p-hydroxybenzoic acid, p-coumaric acid, sinapic acid and benzoic acid.
    Dogra and colleagues (2009) found that the amount of phenolics in the soil was 41% higher in A. conyzoides-invaded areas than in control areas. The pH in the A. conyzoides-invaded areas was slightly higher than in the control areas. The conductivity of the ions was 31% more in the A. conyzoides invaded area as compared to control. Percent organic carbon and organic matter also increased in the invaded area by nearly 49%. The increase in the available nitrogen content was highest among all other nutrients. It increased by 57% in the invaded area. The amount of available phosphorus, potassium and sodium were more by 48%, 38% and 25% respectively in the A. conyzoides-invaded soil as compared to the control soil. The amount of available calcium, magnesium and chloride were more by 37%, 32% and 33% respectively in the A. conyzoides-invaded soil as compared to the control soil (Dogra et al 2009).

    栖地改变: The invasion of these three invasive plant species (A. conyzoides, L. camara, P. hysterophorus) highly reduces the available habitats or niches for the growth of other useful plant species. They are responsible for the loss of productivity and diversity of species in the invaded areas. They drastically alter the structure, function and dynamics of invaded habitats (Dogra, Kohli & Sood 2009).

    生态系统变化: Dogra and colleagues (2009) evaluated the impact of A. conyzoides on the diversity and floristic compositions of native species. It was found that as compared to control, in the Ageratum invaded area:
    • The average number of plant species was reduced by 32% (81 species in the control area as compared to 55 in Ageratum invaded areas);
    • Margalef's index of species richness, alpha species diversity and evenness index were reduced by 37%, 41% and 15%, respectively;
    • The fresh and dry biomass of plants was significantly reduced by 52% and 48%, respectively ;
    • The number of abundant species (N1) and very abundant species (N2) were also significantly reduced; and
    • The value of index of dominance was higher, indicating that communities were homogenous in nature and dominated by a single species (compared with un-invaded communities which showed more heterogeneity).
    It was concluded that invasion by A. conyzoides drastically affects the productivity, composition and diversity of the invaded areas in Shivalik hills of Hamirpur district.

    竞争: A. conyzoides replaces other vegetation including native grasses (Batish 2008; Singh Undated).

    降低本地生物多样性: Dogra and colleagues (2009) found that A. conyzoides, L. camara and P. hysterophorus reduce species diversity and composition in the Shivaliks. The decrease in diversity indices and biomass in the invaded sites show that plant communities become less productive in response to these invasive plant species in the lower Shivaliks of Himachal Pradesh, India (Dogra et al. 2009). Batish (2008) found that A. conyzoides adversely affects biodiversity and checks the growth of grasses and other weeds. A. conyzoides can result in an up to 50% decrease in average dry biomass (grams per meter squared) and can cause an over 30% reduction in total species number (Batish 2008). Singh and colleagues (Undated) found that, compared with controls, native vegetation in A. conyzoides-infested habitats was significantly reduced (including numbers of species, plant density and biomass) especially in wastelands and grassland, indicating that invasion by A. conyzoides reduces plant biodiversity.

    Dogra and colleagues (2009) found that the number of herbs decreased sharply (as compared to other life forms) in the A. conyzoides-invaded areas. Results showed that herbal vegetation was affected maximally as compared to other vegetation types. Major medicinal plants affected by the invasion of A. conyzoides were Murraya koenigii, Dichanthium annulatum, Cynodon dactylon, Trifolium repens, Achyranthes aspera, Adhatoda vasica and Carissa carandas (Dogra et al. 2009).

    West Bengal (India) English 
    农业: A. conyzoides is a crop weed in the plains of Eastern Himalayan region of West Bengal. It is an unwanted plant in the crop land that competes for nutrients, water and space.
    Doon Valley (India) English 
    其它: It creates allergic problems.

    改变林火机制: A. conyzoides introduced from tropical America has expanded at an alarming rate, especially in agricultural fields, along footpaths, road sides and in gardens of heavy peat content. Its dominance in fire-burn areas makes it appear a permanent denizen of India.

    降低本地生物多样性: It is harmful to native floristic composition.
    Dodoma (Tanzania, United Republic of) English 
    传播疾病: Kashina, Mabagala and Mpunami (2003) found that A. conyzoides is a new weed host and disease reservoir of the Tomato yellow leaf curl Tanzania virus near tomato farms in Dodoma, Tanzania. A. conyzoides and Sida acuta are potentially important TYLCTZV reservoirs because they occur in abundant numbers within the tomato farms, they are associated with whitefly vectors, and were found naturally infected with TYLCTZV.



ISSG Landcare Research NBII IUCN University of Auckland